GR- Gaseous Radwaste Flashcards by Timothy DeRossett

What is the purpose of the GR system?

Collects and processes potentially radioactive gases generated within the plant so that exposure of onsite and offsite personnel is kept within acceptable limits

High activity waste gas, containing primarily hydrogen and nitrogen, is collected and stored in the oxygen free system to permit decay of short-lived isotopes

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What comprises the GR system?

A gas surge header, a waste gas surge tank, two waste gas compressors, three waste gas decay tanks and associated piping

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Describe the GR flowpath

Waste gas from surge header is collected in surge tank prior to being filtered and compressed through one of the two parallel and redundant waste gas compressors.

Waste Gas compressors discharge to the combined compressor discharge header which directs the gas to any one of three waste gas decay tanks.

Decayed gas from decay tanks is discharged to the Radwaste building exhaust system through two air operated isolation valves, a gaseous discharge filter, a flow element, a radiation monitor and a flow control valve.

Exhaust is discharged to plant vent where additional radiation monitors exist

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What provides power to GR instrumentation in the RW control room?

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What powers the GR waste gas compressors? Where are they located?

140” RW building

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What does the GA system do for the GR system?

Provides nitrogen that is used for the initial system purge

subsequent purges to allow for maintenance

auto purge from high O2 in surge header

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What would cause the GR gas surge header isolation valves to automatically close? Where does the relief valve on this header discharge to?

Receipt of a CIAS

RW building exhaust

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What powers the motor operated GR gas surge header isolation valve?

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What powers the solenoid operated GR gas surge header isolation valve?

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What is the purpose of the GR Gas Surge Tank?

Absorbs fluctuations in the gas volume entering the system to minimize compressor operating time

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What is the design temperature of the plastic liner in the GR Gas Surge Tank?

200F

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Where is the GR Gas Surge Tank located?

140’ Radwast Building

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What is the purpose of the Gaseous Radwaste compressors?

Pump low pressure gas from the surge tank to the decay tanks for holdup prior to release

Capable of automatic starting and stopping to control surge tank pressure

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When in auto, which GR compressor will start if the mode selector switch is in A-lead, B-stby and there is a high surge tank pressure?

“A” compressor

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When in auto, what would start both GR compressors?

Hi-Hi surge tank pressure

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What is the purpose of the GR Decay Tanks?

Used to store waste gas prior to atmospheric discharge. They serve as a holding area for the gas while it undergoes radioactive decay

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The liner in the GR Decay Tanks is designed for what temperature?

200F

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What situations would cause the GR Decay Tank Discharge Header isolation valves (GRN-UV-34A, 34B) to automatically close? What else closes? How are they reopened?

HR system exhaust fan A and B low D/P
High waste gas discharge flow
High radiation level
High waste gas discharge pressure in the rad monitor supply line

The air supply solenoid valve to flow valve FV-33 closed due to interlock

Manually restored

When is the Gaseous Radwaste system considered out of service?

Valve GRN-V002, surge header isolation valve is closed
OR
All inputs of the surge header are red tagged closed

What is the Hi-hi alarm set point of the GR Oxygen analyzer? What else occurs?

3.75%

Isolates the GR system by stopping the waste gas compressors and an auto dilution of the GR system with nitrogen is initiated

When is the Nitrogen Dilution secured and what affect will it have on oxygen concentration in the GR system? When will the nitrogen auto-dilute the gas surge header, surge tank and decay tanks?

Pressure reaches 25 psig, which should reduce oxygen concentration by 50%

after a 5 minute delay with the HI-HI O2 alarm still in

What system powers the auxiliary relays in the RW control panels?

The 2” diameter GR gas surge header receives gases from what sources?

RDT

Containment refueling failed fuel detector vent

Dry sipping auxiliary pump

Gas stripper

VCT and associated relief

Oxygen analyzer return

How does GR interface with HR?

high activity portion of GR discharges to the HR system

low activity aerated waste gas is also vented from selected equipment

What is the purpose of the GR waste gas compressors? What cools them?

pump low pressure gas from the waste gas surge tank to the waste gas decay tanks for holdup prior to release NC

What is the purpose of the condensate pot tapped off of the GR gas surge header? Where is it located?

to collect condensation from the RDT 77' aux. building west Mech. pen. room

When would the oxygen analyzer that monitors the GR decay tanks sound an alarm?

Oxygen content of 2% or greater

What is the purpose of the GR waste gas surge tank? What is the design temp of this tank? Where is it located?

absorb fluctuations in the gas volume entering the system to minimize waste gas compressor operating time 200*F 140' RW building

When would the GR waste gas compressors auto start and stop?

to maintain waste gas surge tank pressure

Concerning the GR waste gas compressors, at what pressure does the lead and standby compressors start and stop?

lead starts on 3psig stand by starts at 5 psig both stop at 1.5 psig

Nitrogen auto-dilute trips any running GR waste gas compressor. How is the compressor reset?

turning hand switch to stop and then back to auto

At what level does the GR waste gas compressor oil level need to be? How often does each compressor need to be run and why?

.5" above full mark weekly because the compressor will lose oil priming otherwise (compressors are swapped twice a week and they run at least daily)

What is the design pressure of the GR waste gas decay tanks? Where do these tanks relieve to?

380 psig waste gas surge tank

How many GR waste gas decay tanks are normally in service at a time? At what pressure are the tanks swapped? How long must the newly isolated tank remain isolated for prior to chemistry sampling for release?

one at a time ~340 psig 45 days

Where can the GR waste gas decay tanks release to? Where are these tanks located?

RW building exhaust and plant vent stack 140' RW building

How is the GR waste gas decay tank release driven? What is the release rate? When is the release secured, unless maintenance is required?

differential pressure between the tank and the atmosphere 50 SCFM >15 psi if maintenance is required, tanks completely release and are nitrogen purged

Describe the operation of the GR decay tanks isolation valves hand switch in the main control room and in the RW control room. Where are they located?

HS-34B is in the main control room and provides the open permissive to operate UV-34a and 34B from the RW control room hand switch, HS-34A. When HS-34B is put to close, both valves close and can not be operated from the RW control room. 140' RW building

What is required from the Effluents group prior to reopening the GR decay tank isolation valves to start a waste gas release? What does this authorize?

Release permit which tank to release from and a flow rate

What is the purpose of the GR discharge flow control valve? How is it controlled? Where is it located?

controls the rate of waste gas relief to the RW building exhaust header there is a fast and slow mode for manual operation. once the position is set just below the release permit flow rate, the rate is matched on the auto controller and is controlled by the flow element up stream 140' RW building

What protections are in place for RU-12, gaseous radwaste rad monitor? Where is this monitor located?

flow orifice limited to 5 SCFM and a low flow alarm 140' RW building

In the GR system, where can the four O2 analyzers be aligned to?

normally to the waste gas surge header can also be aligned to the waste gas surge tank

Who is notified when there is a loss of operability of the GR system?

immediately unit shift manager and ASAP system process supervisor

When is the GR system considered in-service?

it is considered in service when the system is lined up to any one of the inputs and a compressor is in auto

What are the tech specs related to the GR system?

two O2 monitors must be in service O2 concentration shall be 2% or less